The proposed program is a design for the study of protein undernutrition upon the incidence of aging in the female rat. Specifically, possible neurochemical changes in the hypothalamo-pituitary-gonadal axis affected by protein undernutrition will be evaluated during the entire life span of the rat and compared to those changes known to occur during the onset and duration of the aging process. The control of this vital axis is provided by physiologic stimuli throughout the CNS and by ovarian steroid feedback mechanisms. Extrahypothalamic nerve fibers terminate on hyponthalamic nuclei whereby secretion of the peptidergic release factors is effected. There is evidence for decreased biogenic amines in the aging brain due in part to diminished activity of enzymes for their synthesis and in part, to increased activity of amine degrading enzymes. Should these findings occur in the select hypothalamic nuclei proposed in this study, a basis for hormonal dysfunction may be elicited. The study will include the measure of catecholamines, serotonin and luteinizing hormone release hormone in select hypothalamic nuclei and luteinizing hormone and prolactin in both the pituitary and blood serum of the female rat to determine whether protein nutrition affects the synthesis and release of these agents. Ovarian feedback mechnaisms will also be evaluated to determine whether the dietary paradigm affects estradiol and progesterone release. Finally, biogenic amine turnover rates will be evaluated in the hypothalamic nuclei to determine the effect of protein undernutrition upon the synthesis and utilization of these amines.